1. Field
This document relates to an organic light emitting display.
2. Related Art
In general, an organic light emitting display is a self-emitting display for emitting light due to an electrical excitation of a fluorescent compound. Since the organic light emitting display is driven at a low voltage, is manufactured to be thin, and has a wide viewing angle, a fast response speed, etc., the organic light emitting display has been considered as a next generation display.
The organic light emitting display includes an organic emitting layer between an anode and a cathode. The organic light emitting display forms an exciton, which is a hole-electron pair, by recombining a hole received from the anode and an electron received from the cathode within the organic emitting layer, and emits light by energy generated when the exciton returns to a ground level. The organic light emitting display further includes a hole (electron) injecting layer and/or a hole (electron) transporting layer between the anode or the cathode and the organic emitting layer.
FIG. 1 illustrates a related art organic light emitting display.
Referring to FIG. 1, in an organic light emitting display 100, a thin film transistor 130 is positioned on a substrate 110, and a planarization layer 150 is positioned on the thin film transistor 130.
The thin film transistor 130 includes a semiconductor layer 133, a gate dielectric layer 132, a gate electrode 131, an interlayer dielectric layer 134, a source electrode 135, and a drain electrode 136.
An emission unit 140 is positioned on the planarization layer 150 to be electrically connected to the thin film transistor 130. The emission unit 140 includes a first electrode 141 electrically connected to the drain electrode 136, an organic emitting layer 143, and a second electrode 144.
A dielectric layer 142 is positioned on the first electrode 141 to expose a portion of the first electrode 141. The organic emitting layer 143 is positioned on the exposed portion of the first electrode 141.
A passivation layer 160 is positioned to cover the emission unit 140. An edge portion of the substrate 110 including the passivation layer 160 is attached to a cover substrate 120 with a sealant 170.
FIG. 2 illustrates another example of a related art organic light emitting display.
Referring to FIG. 2, in an organic light emitting display 200, a thin film transistor 230 including a semiconductor layer 233, a gate dielectric layer 232, a gate electrode 231, an interlayer dielectric layer 234, a source electrode 235, and a drain electrode 236 is positioned on a substrate 210. A planarization layer 250 is positioned on the thin film transistor 230.
An emission unit 240 is positioned on the planarization layer 250 to be electrically connected to the thin film transistor 230. The emission unit 240 includes a first electrode 241, a bank layer 242, an organic emitting layer 243, and a second electrode 244.
A passivation layer 260 is positioned to cover the emission unit 240. The substrate 210 including the passivation layer 260 is attached to a cover substrate 220 with a face sealant 270.
Moisture and oxygen penetrating inside the organic light emitting display may damage the organic emitting layer and the electrodes. More specifically, when moisture penetrates from the outside, the moisture reacts with the organic emitting layer and the electrodes through a pin hole formed in a portion of a cathode or an edge between the cathode and a cathode separator, thereby generating hydrogen.
Such hydrogen diffuses into the left and right sides on an interface between the cathode and the organic emitting layer, thereby causing generation of bubbles over the organic emitting layer. As a result, an event in which the cathode is lifted up occurs frequently. Also, when oxygen transmits through the pin hole of the cathode or the edge between the cathode and the cathode separator, an oxide layer is likely to be formed on the cathode at the interface between the cathode and the organic emitting layer. The oxide layer often shields a flow of current.
Referring to FIGS. 1 and 2, the edge portions of the related art organic light emitting displays 100 and 200 include the substrates 110 and 120, the planarization layers 150 and 250, the passivation layers 160 and 260, the sealants 170 and 270, and the cover substrates 120 and 220. Outside moisture and oxygen easily penetrate into the organic light emitting displays 100 and 200 through the interface between the planarization layers 150 and 250 and the passivation layers 160 and 260, thereby deteriorating the organic light emitting displays 100 and 200.